Field of Invention
The present invention relates to a resonant wireless power receiver circuit. Particularly it relates to a resonant wireless power receiver circuit with an adjustable impedance matching circuit. The present invention also relates to a control circuit and the control method of the resonant wireless power receiver circuit.
Description of Related Art
FIG. 1 shows a prior art resonant wireless power system 1, which includes a resonant wireless power transmitter circuit 20 and a resonant wireless power receiver circuit 30, wherein the resonant wireless power transmitter circuit 20 includes a power supply 21, a driver 22, an impedance matching circuit 23, and a transmitter circuit 24. The resonant wireless power receiver circuit 30 includes a receiver circuit 31, an impedance matching circuit 32, a rectifier 33, a DC-DC converter 34, and a load 35.
In FIG. 1, the resonant wireless power transmitter circuit 20 transmits power to a wireless field 40 (for example but not limited to a magnetic field, an electric field, or an electromagnetic field). The wireless power transmitted to the wireless field 40 is received by the resonant wireless power receiver circuit 30 through the resonant effect of the receiver circuit 31 in cooperation with the impedance matching circuit 32, byway of for example but not limited to coupling, induced by, or capturing the wireless power in the wireless field 40. The power received is rectified by the rectifier 33, converted by the DC-DC converter 34, and then provided to the load 35, achieving the wireless power transmission.
FIG. 1B and FIG. 1C show two examples of the combination of the receiver circuit and the impedance matching circuit of the prior art resonant wireless power transmitter circuit shown in FIG. 1A. The receiver circuit 311 and the impedance matching circuit 321 shown in FIG. 1B are configured in parallel for resonance, while the receiver circuit 312 and the impedance matching circuit 322 in FIG. 1C are configured in serial for resonance.
The prior art circuits shown in FIG. 1A-1C has a drawback that the capacitance of the capacitor (e.g. the C1 in FIGS. 1B and 1C) in the resonant wireless power receiver circuit 30 is constant, and therefore the resonant frequency thereof is constant. However, in case of off resonance, or in case the distance between the resonant wireless power receiver circuit 30 and resonant wireless power transmitter circuit 20 is too far, the output voltage of the rectifier 33 may be too low, which could lead to malfunction of the circuits of the following stages (e.g. the DC-DC converter 34 and the load 35 in FIG. 1A).
FIGS. 2A and 2B show another prior art resonant wireless power receiver circuit. The resonant wireless power receiver circuit 30 includes a 1×/2× active rectifier 38 (the details thereof are shown in FIG. 2B). The 1×/2× active rectifier 38 can rectify the wirelessly received AC voltage to a selectable one time (1×) or two times (2×) rectified output voltage to solve the aforementioned low output voltage problem of the rectifier.
However, the prior art circuits shown in FIG. 2A-2B have the following drawbacks. First, the circuit of 1×/2× active rectifier 38 is very complicated and needs a large number of devices. Second, there are only two options for the output voltage. However, as described in the above, the level of the resonant power received by the resonant wireless power receiver circuit 30 is uncertain, and it is possible in certain circumstances that 1× is too low while 2× is too high, such that the circuits of the following stages either cannot function normally or are damaged.
The present invention provides a feedback controlled rectifier output. The present invention is advantageous over the prior art in FIG. 1A-1C in that the low output voltage problem is avoided.
Compared to the prior art in FIG. 2A-2B, the present invention has the advantage of providing a continuously adjustable rectifier output, such that the output voltage of the rectifier is well controlled, not too high and not too low. Further, the present invention uses less components and is more cost effective compared with the prior art.